This invention relates to a rotary switch assembly and more particularly to such a switch assembly adapted to selectively energize one of several different lamps from a single source of current and to assure that the lamp when selected and indexed, is properly aligned in regard to an optical system.
Generally, the prior art has been cognizant of the problem of employing a plurality of back-up bulbs or lamps to permit quick replacement of the one being utilized when a failure occurs. Such techniques provide a minimum down-time for the optical system and enable one to continue using the system because of the additional bulb structures.
It is also apparent that when one employs such back-up lamp sources in a relatively accurate optical system, one must assure that a selected bulb will move in to exact registration with either a lens system and so on, to assure and maintain optical system performance.
In conjunction with such approaches, the prior art is replete with a number of references attempting to solve such problems in different environments.
U.S. Pat. No. 1,105,829 entitled Electric Signalling Mechanism patented on Aug. 4, 1914 by O. D. Plummer, et al. shows a railroad or other signalling system which employs a plurality of lamps rotatably mounted in a lantern housing. The lamps as rotated make contact with a carbon block and are under the control of a motor and electromagnets.
The structure is not critical as the use does not dictate an accurate optical system and hence, wide tolerances can be used in implementing the structure.
U.S. Pat. No. 1,426,181 entitled Automobile Lamp issued on Aug. 15, 1922 to F. E. Gregory shows a rotatable disk carrying a plurality of lamps, each one of which is selected by a quarter turn of the disk.
Still other patents as U.S. 1,455,938 entitled Signal Lantern, U.S. Pat. No. 1,495,656 entitled Auto Headlight and U.S. Pat. No. 1,845,399 entitled Locomotive Headlight, show different index structures for bulb replacement in the typical non-critical environments above described.
Still other patents as U.S. Pat. No. 1,915,081 entitled Focusing Lamp with Focusable Reserve Light Bulb and U.S. Pat. No. 1,978,907 entitled Illuminating Unit and U.S. Pat. No. 2,810,819 entitled Light Projecting Apparatus, attempt to show different techniques and structures for accommodating more than one bulb, which bulb can be switched into position in the event a failure occurs in the one being utilized.
With the event of more reliable and highly sophisticated optical systems the need for a back-up provision during bulb burn-out is still apparent. However, due to the nature of such systems, the alignment of the replacement bulb has to be accurately maintained while providing an easily operable, mechanically reliable and economical indexing system.